[Elecraft] k2 pll and ref osc issues n0xdb

[Foxjazz]

Hello Don,

Don, the call was in the subject line.

Sorry for the confusion. I had the pll circuit working great with all
alignments before starting on phase 3 and putting the ssb board in.

As far as checking parts, the parts were correct when I checked them
the second time, and the pll circuit was working.

tp3 reads within tolerance.  Unfortunately I broke the agc gain
transistor handling the control board, so have to replace. But that
shouldn't affect my issue.

I was doing some voltage readings and found an issue on u5 on the rf
board. pin 1 was 5 volts.

U6: pin 5 was 4v on and 8 was 8 volts.

tp3 reads good, and checked good. However sometimes it feels as if it
doesn't check good because the band - doesn't keep the freq down on
occasions.

N0XDB
-- 


mailto:foxr4 at foxjazz.net


Saturday, April 17, 2010, 5:41:52 PM, you wrote:

> Foxjazz,

> Do you have a real name and a call?  We here on the Elecraft reflector
> certainly would like to know if you do.

> Q6 on what board has the bad resistance reading?  The Q6 on the RF board
> has nothing to do with your PLL problem.

> Is it at TP3 that you are getting a reading of 0.00 kHz?  If not, let's
> start from there.  The most likely source of no reading at TP3 is a 
> problem with RF Board Q19.  And the problem wiht Q19 is most likely 
> soldering somewhere in that circuit.  Turn to the schematic  for the RF
> board sheet 1 and look in the upper left quadrant (up to but not 
> including U4) to identify all the components associated with the PLL 
> Reference Oscillator.  Check the resistance from the source of Q19 to 
> ground - it should be close to 270 ohms - if it is higher, check the 
> lead tinning of RFC14.

> You may have a solder bridge on the thermistor board (notice on the 
> schematic that it is one of the components associated with the PLL Ref
> Osc).   Make a quick check - the voltage on pin 5 of RF Board U6 should
> be very close to 1/2 the voltage on the 8 volt rail (check that at U6 
> pin 8).

> Have you checked to be certain the counter probe is still working 
> properly?  To check that, put the probe into TP2 to read the BFO 
> frequency.  If that also reads 0000.00, you have a problem either with
> the probe or Control Board Q9 and/or Q10.

> Please be specific so we can help you better without creating a 'wild 
> goose chase'.

> 73,
> Don W3FPR

> Foxjazz wrote:
>> Hello Elecraft,
>>
>>   Hello Don,
>>
>>
>>   I had the pll working before I did phase 3 and put the ssb board in.
>>
>>   It was working great, now it isn't. I thought I would run a quick
>>   voltage test before continuing. Now the pll freq is 0.000
>>
>>   I reviewed the test results and re-tinned T5 just to ensure good
>>   conductivity.
>>
>>   When I ran the resistance checks the base resistence of Q6 was at
>>   372 ohms not 100-140 as the book says.
>>
>>   the unit turns on draws 0.24 amps
>>
>>   0.22 without the ssb board in.
>>
>>   Why would the pll circuit just quit working, would q20 have anything
>>   to do with it?
>>
>>   The voltages at q18 are a bit high.
>>
>>
>>
>>
>>
>> I had the pll vol
>>
>>
>>